ISLAMABAD , Pakistan -LRB- CNN -RRB- -- Civilians continued to flee Pakistan 's northwest in droves Monday as government troops prepared to engage Taliban militants in the crisis-hit Swat Valley .

Thousands of displaced Pakistani civilians have flooded refugee camps .

More than 360,000 Pakistanis have fled their homes since May 2 , the United Nations has reported .

`` Obviously more people are on the move , '' said Ariane Rummery , a spokeswoman for the U.N. human rights commissioner . `` Not everyone is registered . ''

Thousands of vehicles fled Swat Valley on Sunday , where up to 15,000 Pakistani troops are preparing to move against approximately 5,000 Taliban militants , a regional official said .

In neighboring areas , Pakistan 's military is continuing an offensive against the Taliban along its western border with Afghanistan , a military statement released Sunday said . Watch the latest on the conflict ''

The military has been releasing regular reports saying it has killed Taliban militants in the region , but it has produced little evidence of the successes it claims . Journalists have not been permitted to observe the offensive and the army has not shown bodies of the militants it says it has killed .

Curfews have been imposed in the conflict zone , but are relaxed periodically to allow civilians to travel . It is not unusual now to see rickshaws and cargo trucks filled with fleeing civilians , rolling down Pakistan 's main east-west highway .

Vehicles are not allowed back into the region , which has led to a shortage for those trying to leave .

Meanwhile , at least 25 boys stranded at the Khpal Kor Foundation orphanage in Swat Valley had to flee the district capital , Mingora , on foot Sunday , according to director Mohammed Ali .

He said local government officials told him there were no vehicles to evacuate the children .

The 175-kilometer -LRB- 110-mile -RRB- journey from Mingora to the western city of Peshawar normally takes about three hours by car . The boys walked for several hours , but had to spend the night in a madrassa -- a religious school -- outside of Mingora , because authorities had re-established the curfew .

Camps for the displaced have sprouted up throughout the country 's northwest , with hospitals and humanitarian groups struggling to keep pace .

In other developments , a suicide car bomber attacked a Pakistani paramilitary checkpoint outside Peshawar on Monday , killing a Frontier Corps soldier and three civilians , said Ali Sher Khan , a Corps spokesman .

Troops fired on the suspicious vehicle as it approached , according to Khan .

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U.N. : More than 360,000 Pakistanis have fled their homes since May 2

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15,000 Pakistani troops preparing to move against militants in Swat Valley

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Tens of thousands of civilians have fled as the military campaign intensifies

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Pakistan continuing offensive against Taliban along border with Afghanistan